This invention pertains to collecting liquid, particularly water, in the vicinity of subterranean structures and providing for its conveyance to a safe place as regards the subterranean structure. It is particularly useful adjacent up-standing subterranean walls where it provides thermal insulation to reduce heat loss by conduction through the wall.
When constructing a below grade concrete wall for a building or other structure, certain problems have arisen in conventional construction practice. Walls which are built without insulation are energy wasters. Also, any water leakage through the wall can damage both the wall and the interior of the building. So it is important to control transmission of water through the wall to the building interior, and to control transmission of heat through the wall to the surrounding soil outside the building. These issues are of even greater significance where habitable area is desired below ground level.
When insulating walls, insulating on the exterior portion of these foundation walls usually proves to be the most advantageous. Most insulation materials and products are combustible and will ignite and burn readily, even though some are treated for fire retardation. With the insulation on the exterior surface of the subterranean wall, this is not a problem; and so insulation is usually put on the exterior surface of the wall, with one major reason being fire safety.
The exterior subterranean environment, though, presents its own series of problems and requirements of an insulation material, which must be met in order for the insulation to functionally retain its insulating value. The main requirements are that the insulation must have an adequate resistance to compressive load, and it should not absorb a significant quantity of water. If the insulation compresses appreciably, or if it absorbs a significant amount of water, its insulating value is reduced. Particularly if the insulation absorbs water, and if freeze and thaw conditions exist, the expansion and contraction of moisture particles can damage the insulation.
As mentioned earlier, it is desirous that walls both be insulated and have water kept away from them, to prevent problems of excessive heat loss, and moisture damage.
In order to prevent water leakage and/or hydrostatic pressure on subterranean walls, in most cases, a drainage system is used in the vicinity of the wall. Hydrostatic pressure is caused by water in the surrounding soil which exerts forces on the wall. This force, if excessive, could crack or severely damage the wall.
Conventional drainage systems are time consuming to install and are relatively expensive. One conventional system uses drain tile and crushed rock around the footings of the wall. This is effective only if the soil permeability (K-cm/sec) is high enough to allow the water to flow to and into the system. If not, and commonly, water could leak into the basement or build up hydrostatic pressure against the wall, as this system does not provide a barrier to prevent ground water from reaching the wall.
Particularly during heavy rains, or during winter or spring melting of snow, soils often are not permeable enough to permit the water to efficiently seep through and into the footing drainage system.
Walls can be more or less waterproofed with certain commercially available materials, but these materials are not effective to stop water leakage should a crack develop in the wall. And, given time, many walls develop cracks. So it is highly desirable that water contact with the wall surface be minimized, and it is especially desirable that water be prevented from reaching the wall surface.
Certain products are commercially available to convey water into drain tile at the footings, but they are not capable of concurrently providing insulation.
U.S. Pat. No. 3,654,765 Healy et al teaches a drainage manufacture using a core member of "foamed polystyrene". But many foamed polystyrenes are unacceptable because of excessive moisture absorption, and so Healy et al does not solve the problem of providing concurrently, insulating properties, lack of water absorption, and conveyance of moisture away from the wall. Likewise the Healy et al patent teaches, as regards the fabric covering, only that it be pervious, and that it have "suitable mesh and thickness that solid particles will be held back or pass through one opening but will not remain in a position so as to clog the opening."
U.S. Pat. No. 4,309,855 Pate et al teaches a channelled polystyrene foam board having a covering of a synthetic resin film having very small capillaries which extend through the film. At the base of the board is a bead pack for conveying water from the board to the drain pipe.
U.S. Pat. No. 4,538,387 Barnett et al further teaches using a fibrous material quilted to the fabric covering.
It is an object of the invention to provide an improved product for subterranean drainage.
It is another object to provide such a product which concurrently provides thermal insulation.
It is yet another object to provide an improved method of providing subterranean insulation and drainage.
It is still another object to provide a improved unitary product which concurrently provides subterranean drainage, thermal insulation, and low water absorption; such that all three features are obtained by the installation of the single unitary product, or a series of substantially similar unitary products.